Reticulated themoplastic rubber products

ABSTRACT

Thermoplastic rubber containing minor amounts of olefin polymer is directly extrusion-formed into reticulated film.

This application is a continuation-in-part of application Ser. No.179,593, filed Aug. 19, 1980, now U.S. Pat. No. 4,329,309, which is acontinuation-in-part of application Ser. No. 67,850, filed Aug. 20,1979, now abandoned, which is a continuation-in-part of application Ser.No. 36,726, filed May 5, 1979, now U.S. Pat. No. 4,305,990, which is adivision of application Ser. No. 848,439, filed Nov. 3, 1977, now U.S.Pat. No. 4,173,612.

The invention relates to reticulated film comprising thermoplasticrubber and an olefin polymer, which has valuable utility as the elasticmember in elasticized disposable diapers.

BACKGROUND OF THE INVENTION

Thermoplastic rubber is a relatively new type of polymeric compositionthat has become commercially available within the past decade or so.These polymers have the useful property of behaving like rubber atnormal use temperatures, without the need for vulcanization. And becausethey are not vulcanized, they can be processed by many of the normalthermoplastic resin procedures at elevated temperatures.

One serious problem has been encountered, however, in attempts toextrude film from thermoplastic rubber. Either because of too low meltstrength, or excessive notch sensitivity, or both, pure thermoplasticrubber does not draw well when extruded into thin films. The preferredway to extrude films from thermoplastic polymers is to draw the extrudedweb at a rate of speed faster than the rate at which the molten materialis ejected from the die. This causes a reduction in thickness.Typically, this reduction in thickness will be as much as three-fold oreven more.

I have found, however, that when one attempts to extrude a film frompure thermoplastic rubber, the web cannot be drawn down at all. In fact,in many cases the web must be drawn at a rate of speed slower than theextrusion rate, to thereby produce a film having a thickness or gaugegreater than the die gap. This is undesirable because the throughputrate is slow, and because gauge variations are magnified. And further, Ihave not been very successful in producing any films at all of purethermoplastic rubber at thicknesses much less than about 10 mils becauseof an excessive tendency of the extruded webs to tear.

In my said earlier applications, I disclosed the addition of amorphouspolypropylene to thermoplastic rubber to improve the processability ofsaid rubber such that it can readily be extruded into films, while stillretaining the characteristic properties of rubber. In application Ser.No. 67,850, I disclosed that thermoplastic rubber containing amorphouspolypropylene can be directly extrusion formed into reticulated film ina continuous process which employs a pair of counter-rotating rolls, thefirst roll being a smooth roll and the second having a resilient surfaceengraved with a series of intersecting grooves.

It has now been discovered that, in addition to amorphous polypropylene,a number of other olefin polymers can be employed as additives tothermoplastic rubber in a continuous, direct extrusion process for theproduction of reticulated film having exceptionally valuable utility asthe elastic member in elasticized disposable diapers.

SUMMARY OF THE INVENTION

A mixture of the thermoplastic rubber and olefin polymer is extruded asa molten sheet directly onto a smooth, heated roll. The smooth roll isin contact with a second roll to form a nip. The second roll is cooledand has a resilient surface that is engraved with a series ofintersecting grooves. The second roll preferably has a slightly higherperipheral speed then the first roll. As the molten sheet passes throughthe nip between the two rolls, the molten sheet fills the saidintersecting grooves and forms an open reticulated sheet, which issolidified on the second roll and then removed therefrom. Thereticulated sheet produced thereby has exceptional utility as theelastic member in an elasticized disposable diaper.

THE PRIOR ART

It is known to add thermoplastic polymers in varying proportions tothermoplastic rubbers. It has been suggested to blend "polypropylene"(meaning isotactic or crystalline polypropylene), polystyrene,polyetheylene, ethylene-vinyl acetate copolymer, and polyurethane withthermoplastic rubber.

Kindseth, in U.S. Pat. No. 3,085,292, describes a process for makingopen mesh sheeting by extruding thermoplastic resin into the nip of apair of counterrotating rolls, at least one of which is engraved with apattern of intersecting grooves.

Kalwaites, in U.S. Pat. No. 3,881,381, and Kalwaites et al., in U.S.Pat. Nos. 3,632,269, 3,666,609, and 4,013,752, disclose a process forforming reticulated film of isotactic polypropylene or other orientablethermoplastic polymer by embossing a film of such polymer at elevatedtemperature with a resilient embossing roll while simultaneously coolingand drafting the resulting reticulated film.

Harper, in U.S. Pat. No. 4,076,669, discloses blends of amorphouspolypropylene in thermoplastic rubber.

Korpman, in U.S. Pat. No. 4,062,995, discloses the production ofreticulated film from a blend of thermoplastic rubber and a tackifyingresin.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view in elevation of an arrangement of apparatussuitable for producing reticulated thermoplastic rubber sheet material;

FIG. 2 is an enlarged cross-sectional view of the embossing roll havinga resilient surface that is used in the process for making reticulatedthermoplastic rubber sheet material; and

FIG. 3 is a view in perspective of the reticulated sheet materialproduced in accordance with the invention.

DETAILED DESCRIPTION OF THE INVENTION

The sheet material of the invention contains thermoplastic rubber and anolefin polymer. The thermoplastic rubbers contemplated for use in theinvention are known materials. They are block copolymers having blocksof polybutadiene or polyisoprene, and blocks of polystyrene. A reviewarticle discussing these materials is "Structure And Properties of BlockPolymers And Multi-phase Polymer Systems: An Overview Of Present StatusAnd Future Potential", by S. L. Aggarwal, Polymer, Vol. 17, November1976, pages 938-956. Two representative types of thermoplastic rubbersare the linear block copolymers (A-B-A) having a mid-block ofpolybutadiene or polyisoprene and end-blocks of polystyrene, and the"star" or "radial" block copolymers having from 4 to 20 "arms" connectedto a common center. Each arm is an A-B block copolymer, the innerportion being polybutadiene or polyisoprene, with the outer portionbeing polystyrene.

The typical thermoplastic rubber contains discrete polystyrene domainsin a rubbery matrix. Apparently the polystyrene domains act in a manneranalogous to conventional chemical crosslinks. The resulting rubber actsas though it has been vulcanized, even though no chemical crosslinks arepresent.

When the thermoplastic rubber is heated to about 200° F., thepolystyrene domains begin to soften, and at temperatures of the order of300° F. to 400° F., the thermoplastic rubbers can be melt processed bymechanical working in a manner analogous to conventional thermoplasticcompositions. Upon cooling, the discrete polystyrene domains arereformed, and the material again exhibits rubbery elastomericproperties.

The material that is employed with the thermoplastic rubber is an olefinpolymer. The olefin polymer does the following to the mixture ofthermoplastic rubber plus olefin polymer:

(a) It permits a draw ratio of greater than 1, as evidenced by theability of draw down extruded sheets of the mixture to a thickness lessthan the extruder die gap; and

(b) It renders the melt sufficiently tack-free to permit continuousextrusion forming.

In addition to these processing characteristics, the reticulated filmproduct exhibits the below-listed properties that make it especiallyuseful as the elastic member in an elasticized disposable diaper:

(a) Good balance of elasticity, modulus, and creep resistance so thatthe diaper will be gathered sufficiently for the duration of normal useto ensure a good fit, but the force per unit area is relatively low sothat there is less redness, irritation, and marks on the skin than whena solid, narrower ribbon of elastic is used to impart the same overallelastic strength; and

(b) Anti-blocking properties prevent or significantly reduce sticking tothe diaper's backing film and facing sheet, thereby resulting in a lessstiff, more conformable product than would be obtained if thereticulated film of U.S. Pat. No. 4,062,995 (Korpman) were used (thisadvantage is obtained when the reticulated film is held in place in thediaper by an intermittent pattern of adhesive binder extending throughthe openings in the film from the backing film to the facing sheet).

The olefin polymers that are employed with the thermoplastic rubber toimpart the foregoing properties include isotactic polypropylene,polyethylene, amorphous polypropylene, polybutylene, ethylene/vinylacetate copolymer, ethylene/ethyl acrylate copolymer, ethylene/methylacrylate copolymer, polystyrene, and the like.

Amorphous polypropylene is essentially atactic polypropylene having anisotactic content of not more than about 20 weight percent, andpreferably not more than about 10 weight percent.

The olefin polymer is employed in an amount sufficient to improve theprocessability of the thermoplastic rubber when extruding thin films orsheets. Such improvement is evidenced by the ability to draw downextruded webs of the rubber/olefin polymer mixture to thereby producesheets or films having thicknesses less than the die gap. Further, thepressure in the extruder and die is greatly reduced, which permits moreeconomical operation. The exact minimum amount of olefin polymer whichmust be employed in which must be employed in order to obtain theadvantages of the invention varies somewhat from case to case, but it isusually of the order of about 10 weight percent, based on weight ofrubber plus olefin polymer, although the proportion may be as low asabout 5 weight percent (on the same basis) in some cases. The upperlimit of olefin polymer will also vary from case to case, depending onthe nature of the ingredients. At proportions above about 35 weightpercent (on the same basis), a significant reduction in thecharacteristic rubbery elastomeric properties of the product begins tooccur. This may be acceptable in some cases, and not in others, Thus,the upper limit of olefin polymer would be that point at which theproduct still retains significant rubbery elastomeric characteristics.

Other conventional materials, employed in the usual amounts, can beemployed in the mixture for their known purposes. Such materials includepigments, anti-blocking agents, stabilizers, anti-oxidants, ultravioletstabilizers, bonding aid, and the like.

The reticulated film of the invention is preferably produced byextruding a thin film of a mixture of the olefin polymer andthermoplastic rubber directly onto a forming apparatus (describedbelow). Conventional extrusion apparatus can be employed. Melttemperatures will usually be within the range of from about 275° toabout 500° F., and preferably from about 325° to about 450° F. Becauseof the radically different melting points and melt viscosities of thetwo (or more) materials, thorough mixing is more difficult than theusual case of mixing two different thermoplastic polymers. In some casesit has been found that mixing is enhanced by cooling the extrudingscrew. Extruder screws that are specifically designed for effectivemixing are available, and may be preferred for efficient commercialoperation.

The extruded film is formed into a reticulated sheet material. Apreferred way to do this is to form the reticulated sheet directly fromthe extruded film without collecting the film as an intermediateproduct. This can be done by the process which is schematicallyillustrated in the drawings.

Referring to the drawings, a mixture of thermoplastic rubber and olefinpolymer is extruded in the form of a thin sheet 12 of molten materialthrough a conventional slot die 14. The still molten sheet 12 iscollected on a heated rotating roll 16 having a smooth surface. Theheated smooth roll 16 has a predetermined peripheral speed. Thetemperature of the heated smooth roll 16 is such that the sheet 12 ismolten an formable when the sheet 12 reaches the nip 17 between the roll16 and a second roll 18. The second (embossing) roll 18 is in contactwith the smooth roll 16 at the said nip 17 between the two rolls. Theembossing roll 18 is cooled, and has a resilient engraved surface. Theengraving is in the form of continuous recessed areas 20 surroundingdiscontinuous raised areas 21. For instance, a preferred engravedpattern has a first series of grooves running circumferentially aroundthe surface of the embossing roll 18, and a second series of groovesrunning perpendicular to and intersecting the first series of grooves.The said second series of grooves are parallel to the longitudinal axisof the embossing roll 18. They are shown in cross-section andexaggerated form as 20 in the drawings.

The sheet 12 transfers from the smooth roll 16 to the embossing roll 18at the nip 17 between the two rolls. The embossing roll 18 is cooled sothat the thermoplastic rubber solidifies while it is in contacttherewith. The embossing roll 18 preferably is rotating at a slightlyhigher peripheral speed than the smooth roll 16. In some cases, the tworolls 16, 18 can rotate at the same speed, and in others, the embossingroll 18 can be slightly slower than the smooth roll 16. There is awiping action at the nip 17 which forces substantially all of the moltensheet 12 into the grooves 20, as is shown in enlarged and exaggeratedform in FIG. 2.

The sheet begins to solidify in the form of a netting or reticulatedsheet 22 while it is in contact with the embossing roll 18. The nettingwill have the same structure or pattern as the engraved grooves on theroll 18. A typical reticulated sheet product 22 is illustrated in FIG.3.

A convenient way to remove the reticulated sheet 22 from the embossingroll 18 is to remove it onto a take-off roll 24, which is also cooled.The take-off roll 24 forms a nip 25 with the embossing roll 18, and canbe rotating at about the same peripheral speed, slightly slower, orslightly faster than the embossing roll 18.

The surface of the heated smooth roll 16 is kept at a temperature suchthat the extruded sheet 12 is molten when it reaches the nip 17, as isevidenced by the sheet being able to form into a reticulated sheet uponcontact with the embossing roll 18. Exact surface temperatures will varyfrom case-to-case, depending on the nature and temperature of theextruded sheet, the peripheral speed of the roll, and similar factors,but will usually be of the order of about 175° F. to about 350° F., andpreferably about 200° F. to about 250° F.

The surface temperature of the embossing roll should be cool enough tosolidify the formed reticulated sheet so that it can be taken off theroll and handled. Typical surface temperatures of the embossing roll arefrom about 100° F. to about 190° F., and more usually 140° F. to 170° F.

The take-off roll can be cooled to facilitate removal of the reticulatedsheet, and to complete the solidification of the reticulated sheet,where needed.

Throughput rates of from about 10 to about 60 feet per minute have beenused successfully.

The embossing roll preferably has a slightly higher peripheral linearspeed than the heated smooth roll. The speed differential is usuallywithin the range of from 1 or 2 percent to about 15 to 20 percentgreater, with about 3 to about 6 percent greater being more usual. Thepercentages are based upon the speed of the embossing roll. Similarspeed differentials are employed when the embossing roll has a slightlylower peripheral linear speed than the heated roll.

In the Examples below, the following polymers were employed:

A. THERMOPLASTIC RUBBERS

"Solprene P414" was a 60/40 butadiene/styrene radial block copolymer,and "Solprene P418" was an 85/15 isoprene/styrene radial blockcopolymer. These materials are further characterized as follows:

    ______________________________________                                                     Solprene P414                                                                            Solprene P418                                         ______________________________________                                        Molecular weight                                                                             150,000      300,000                                           Specific gravity                                                                             0.95         0.92                                              Melt flow, 5 kg @ 200° C.                                                             2.2          2.2                                               Inherent viscosity                                                                           0.80         1.16                                              Solution viscosity, cps.                                                       20% wt in toluene                                                                           230          900                                                25% wt in toluene                                                                           --           2300                                              Physical Properties                                                           Compression Molded 2 Minutes At 300° F.                                100% modulus, psi                                                                            600          140                                               Tensile at break, psi                                                                        4000         1400                                              Elongation, %  750          1050                                              Shore A Hardness                                                                             90           34                                                ______________________________________                                    

B. OLEFIN POLYMERS

1. "AFAX 900-C-P" is an amorphous polypropylene having the followingproperties:

    ______________________________________                                                      Typical Value,                                                                AFAX 900-C-P                                                                            Test Method                                           ______________________________________                                        Viscosity, cps.                                                                at 350° F. (177° C.)                                                           5500        Brookfield                                                                    Thermosel                                          at 375° F. (191° C.)                                                           4000        Brookfield                                                                    Thermosel                                         Needle penetrations, mm/10                                                                    16          ASTM D 1321-65                                    Ring-and-ball softening                                                       point, °F., (°C.)                                                               310(154)    ASTM D 2398-68                                    Density, lbs/gal (kg/liter)                                                    at 75° F. (24° C.)                                                             7.2(0.86)                                                      at 375° F. (191° C.)                                                           6.1(0.73)                                                     Normal Application                                                                            350-375                                                       temperature: °F. (°C.)                                                          (177-191)                                                     Flash Point, °F. (°C.)                                                          500(260)    ASTM D 92                                         Ash content, ppm                                                                              10          Hercules P-67-3                                   Glass Transition                                                                              -6(-21)     duPont 990                                                                    thermal                                           temperature, °F. (°C.)                                                          13.5(7.4)   analyzer                                          Heat of fusion, Btu/lb,                                                                       0.66        duPont 990                                                                    thermal                                           (cal/gm)                    analyzer                                          Heat capacity, Btu/lb/°F.                                                                          Perkin-Elmer                                                                  DSC-2                                             ______________________________________                                    

2. DQDE-1868 is an ethylene/vinyl acetate copolymer having about 17-18percent vinyl acetate.

3. "Elvax" 460 is an ethylene/vinyl acetate copolymer having a MeltIndex (by ASTM D 1238) of 2.2-2.8 and a vinyl acetate content of 17.5 to18.5 weight percent.

4. "Petrothene" UE 630 is an ethylene/vinyl acetate copolymer having 17weight percent vinyl acetate and a Melt Index of 0.5.

5. Shell polybutylene 0300 is a poly(butene-1) having a Melt Index of4.0.

EXAMPLE 1

Reticulated sheet material was produced from the following formulation:

    ______________________________________                                                         Parts, by weight                                             ______________________________________                                        Solprene P418      78.8                                                       AFAX 900-E-P       10                                                         Ethylene/Vinyl Acetate                                                        Copolymer (DQDE = 1868)                                                                          10                                                         Kemamide E         1                                                          Ionol (antioxidant)                                                                              0.2                                                        ______________________________________                                         (1) A fatty acid amide used as an antiblocking agent.                    

The arrangement of apparatus illustrated in FIG. 1 was used. Theextruder was a 21/2 inch Egan having an L:D ratio of 24:1. The die wasstopped to give a 20 inch wide die. The die gap was 15 mils. Theextruder conditions were the following:

    ______________________________________                                        Zone 1 °F.   300                                                       Zone 2 °F.   350                                                       Zone 3 °F.   360                                                       Zone 4 °F.   410                                                       Adaptor °F.  458                                                       Die 1 °F.    450                                                       Die 2 °F.    440                                                       Die 3 °F.    440                                                       Melt temperature °F. (approx.)                                                             375                                                       Screw RPM            30                                                       Barrell Pressure, psi                                                                             2600-2700                                                 ______________________________________                                    

The roll conditions were the following:

    ______________________________________                                                      Peripheral                                                                            Surface                                                               speed, feet                                                                           temperature,                                                          per minute                                                                            °F.                                              ______________________________________                                        Heated smooth roll                                                                            12        220                                                 Embossing roll   121/2    150-160                                             Take-off roll   12         35                                                 ______________________________________                                    

The embossing roll had a surface made of silicone rubber, and anengraved pattern of grooves. The individual grooves had a cross-sectionthat was approximately square, 19 mils on a side. There were 20 groovesper inch in the machine direction and 16 grooves per inch in the crossdirection.

The pressure at the nip between the heated smooth roll and the embossingroll was about 40 pounds per linear inch, and the pressure at the nipbetween the embossing roll and the take-off roll was about 20 pounds perlinear inch.

Typical reticulated sheets made in this manner have machine directionfilaments with diameters of about 14.4 mils, cross direction filamentswith diameters of about 19.8 mils, power pull.sup.(1) on the first cycleof 0.56 at 100% elongation, and power pull after the 10th cycle of 0.52with a 10 percent elongation.

The above-described netting makes an excellent leg reinforcement forelastic disposable diapers.

In the preceding example, the heated smooth roll had a diameter of 8inches and a chromed steel surface, the take-off roll had the samediameter and the same surface, and the embossing roll had a diameter of6 inches.

The pressure at the nip between the heated smooth roll and the embossingroll is enough to penetrate the thin sheet and form the sheet into anopen reticulated structure of intersecting filaments corresponding tothe pattern of grooves on the embossing roll. The exact pressure has notbeen found to be narrowly critical, and pressures of the order fromabout 10 to about 150 pounds per linear inch, and more preferably fromabout 20 to about 55 pounds per linear inch, have been found to beacceptable.

EXAMPLE 2

Reticulated sheet material was produced from the following formulation:

    ______________________________________                                                        Parts, by weight                                              ______________________________________                                        Solprene 418      66.9                                                        Solprene 414      20.0                                                        Elvax 460 or UE 630                                                                             8.0                                                         Shell Polybutylene 0300                                                                         4.0                                                         Kemamide E        0.8                                                         Ionol (anti-oxidant)                                                                            0.2                                                         Irganox 1010 (anti-oxidant)                                                                     0.2                                                         ______________________________________                                    

The arrangement of apparatus illustrated in FIG. 1 was used. Theextruder was a 21/2 inch Welex having an L:D ratio of 30:1. The die wasstopped to give an 18 inch wide die. The die gap was 15 mils.

The extruder conditions were the following:

    ______________________________________                                        Zone 1, °F.                                                                              301                                                         Zone 2, °F.                                                                              353                                                         Zone 3, °F.                                                                              381                                                         Zone 4, °F.                                                                              398                                                         Zone 5, °F.                                                                              398                                                         Melt, °F.  404                                                         Adaptor, °F.                                                                             438                                                         Die 1, °F. 443                                                         Die 2, °F. 452                                                         Front Pressure, psi                                                                             2955                                                        Adaptor Pressure, psi                                                                           1670                                                        Screw RPM         25                                                          ______________________________________                                    

The roll conditions were the following:

    ______________________________________                                                      Peripheral                                                                    Speed, feet                                                                           Surface Temp.                                                         per minute                                                                            °F.                                              ______________________________________                                        Heated Smooth Roll                                                                            16.5      243                                                 Embossing Roll  18        153-158                                             Take-off Roll   18         71                                                 ______________________________________                                    

The embossing roll pattern and the pressure conditions in the rolls werethe same as those described above in Example 1.

The reticulated sheet material thus produced required a pull of 0.7±0.1pounds to stretch a 3/4-inch wide strip to 100 percent elongation. Thesheet had a weight of 0.33 pounds per square yard. When a 3/4-inch wideby 1 inch long specimen is stretched in an Instron tester to 100 percentelongation at a pull rate of 20 inches per minute, and then released,the instantaneous elongation set is less than 15 percent.

The elastic reticulated sheet material made in accordance with theinvention is especially useful as the elastic member is an elasticdisposable diaper. For this application, a number of potentiallyconflicting requirements must be balanced. For instance, reticulatedsheet material having a relatively high percentage of open area isdesirable for "strike-through" bonding of the elastic in the diaper. Instrike-through bonding, several glue lines (e.g., 3 to 5) are laid downlongitudinally on the backing film of the diaper, the elasticreticulated sheet material, in a stretched condition, is superimposed ontop of the glue lines, and the facing sheet is then placed on top of theelastic. The backing sheet is thus bonded to the facing sheet throughthe elastic reticulated sheet material. In order to achieve a relativelyfast line speed in the diaper-producing machine, the open area of theelastic reticulated sheet material should be at least about 40 percent.

In order to achieve the desired elastic strength, however, there must bea certain minimum total cross-sectional area of longitudinal filamentsin the reticulated sheet material. It has been found that there shouldbe sufficient longitudinal filaments of sufficient cross-sectional areato yield a tensile strength at 100 percent elongation of about 0.4 toabout 1 pound for a 3/4-inch wide strip.

Balancing these two requirements, the preferred elastic reticulatedsheet material for the diaper application has an open area of from about40 percent to about 75 percent.

The requirement for the cross filaments appear to be much less critical.Sufficient cross filaments to stabilize the reticulated sheet materialduring processing is all that is required.

The materials described in the Examples above illustrate preferredmaterials for the diaper application.

What is claimed is:
 1. Reticulated sheet material consisting essentiallyof a mixture of (a) thermoplastic rubber comprising a block copolymer ofstyrene and butadiene or isoprene, and (b) sufficient olefin polymer toimprove the processability of said block copolymer, as evidenced by theability to achieve a draw ratio of greater than one while extruding saidmixture of (a) and (b), wherein said olefin polymer is selected from thegroup consisting of isotactic polypropylene, polyethylene, amorphouspolypropylene, polybutylene, ethylene/vinyl acetate copolymer,ethylene/ethyl acrylate copolymer, ethylene/methyl acrylate copolymer,and polystyrene, and wherein said reticulated sheet material has an openarea of from about 40 percent to about 75 percent, and tensile strengthat 100 percent elongation of about 0.4 to about 1 pound for a 1/2-inchwide strip.
 2. The reticulated sheet material of claim 1 wherein saidblock copolymer is a radial block copolymer of styrene with butadiene orisoprene.
 3. The reticulated sheet material of claim 1 wherein theolefin polymer is employed in an amount within the range of from about 5to about 35 weight percent, based on weight of block copolymer plusolefin polymer.
 4. The reticulated sheet material of claim 1, 2 or 3wherein the olefin polymer is amorphous polypropylene.
 5. Thereticulated sheet material of claim 1, 2 or 3 wherein the olefin polymeris polybutylene.
 6. The reticulated sheet material of claim 1, 2 or 3wherein the olefin polymer is ethylene/vinyl acetate copolymer.
 7. Thereticulated sheet material of claim 1, 2 or 3 wherein the olefin polymeris polybutylene plus ethylene/vinyl acetate copolymer.